198001723 - F021 ABS NOT WORKING / (ONE WHEEL LOCKED)

When the brakes are operated briskly and suddenly (emergency braking) the ABS does not work and, as a result, one of the wheels locks
The locking of one of the wheels may, in certain circumstances, be a normal reaction of the system (see operation of the ABS system). This is possible, in particular, on uneven roads
Test results
1CHECK USING DIAGNOSTIC EQUIPMENTAll OKProblems encounteredOperation
Connect the Examiner diagnostic equipment to the diagnostic socket.Check:- that there are no faults in the ABS control unit;- the plausibility of all the parametersMove on to Step 21. Error detected in the control unit2. No communication with the control unit1. Continue following the instructions on the diagnostic equipment2. Restore connection between the ABS control unit and the diagnostic connector see    See E7020 ABS
2ACTIVE DIAGNOSIS WITH DIAGNOSTIC EQUIPMENTAll OKProblems encounteredOperation
Keeping the Examiner diagnostic equipment connected carry out the active diagnosis of:- pump motor;- solenoid valvesMove on to Step 3Fault detected in one of the solenoid valvesReplace the electrohydraulic unit - ABS electronic control unit    Op. 3340A12 ABS HYDRAULIC AND ELECTRONIC CONTROL UNIT - R.R.
3CHECK FOR PRESENCE OF AIRAll OKProblems encounteredOperation
Check for the presence of air in the systemMove on to Step 4Presence of air in the systemBleed the air from the system
4CHECK ON PIPES / HOSES AND BLEED BRAKESAll OKProblems encounteredOperation
Visually inspect that there are no bends or constrictions in the brake pipesMove on to Step 5Presence of bends or constrictionsReplace the section of pipe affected by the problem
5BRAKE CALIPER CHECKAll OKProblems encounteredOperation
Check the sliding of the brake caliper control pistonsEnd of diagnosis1. Front caliper pistons seized2. Rear caliper pistons seized1. Replace the front brake calipers    Op. 3310A30 FRONT BRAKE CALIPER (ONE) - R.R 2. Replace the rear brake calipers    Op. 3310B36 REAR BRAKE CALIPER (ONE), LEFT OR RIGHT - R.R